Semiconductor Element and Fabrication Method Thereof

ABSTRACT

A semiconductor element has a metal protective layer and a metal oxide protective layer formed on the substrate to prevent the Si substrate surface from forming an amorphous layer; and a transition layer to reduce lattice difference between the metal oxide protective layer and the III-IV-group buffer layer, thus improving crystal quality of the III-IV-group buffer layer. A fabrication method can avoid formation of amorphous layers and cracks surrounding the Si substrate surface. A light-emitting diode (LED) element or a transistor element can be formed by depositing a high-quality multi-layer buffer structure via PVD and forming a GaN, InGaN or AlGaN epitaxial layer thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims priority to,PCT/CN2016/097757 filed on Sep. 1, 2016, which claims priority toChinese Patent Application No. 201510629914.9 filed on Sep. 29, 2015.The disclosures of these applications are hereby incorporated byreference in their entirety.

BACKGROUND

Physical vapor deposition (PVD) is an easy-to-operate process thatconsumes little raw material and causes little environmental pollution.Moreover, the film formed via PVD is dense and even, and is tightlybonded to the base. With these advantages, PVD is increasingly appliedin fabrication of semiconductor elements, in particular, to fabricationof bottom layers of epitaxial wafer. For example, by depositing an AlNlayer as the buffer layer, defects from lattice mismatch and thermalmismatch between the substrate and the epitaxial layer can be minimized,and the stress caused therefrom can be eased, thus improving quality ofthe semiconductor element.

Compared with chemical vapor deposition (CVD), atoms sputtered from PVDhave higher energy (in general 10˜20 eV) and migration ability.Therefore, a high-quality buffer layer can be deposited via PVD. Inparticular, for materials with strong bond energy like AlN, film layersdeposited via PVD are better than those deposited with MOCVD. However,direct growth of AlN on the Si substrate surface via PVD is likely toform an amorphous silicon oxide layer at the contact surface between thesubstrate and AlN, leading to poor quality of subsequently-formed AlNlayer and the defects below: as a stress buffer layer, the AlN layer hasinconsistent stress release ability, and the stress is concentrated inthe amorphous silicon nitride layer of the contact layer, resulting incracks that degrade quality of semiconductor elements; in addition, theAlN layer with lower density would generate holes, through which,Gallium would corrode the Si substrate in subsequent chemical vapordeposition of Ga-containing nitride. This would form pits and lead topoor performance of semiconductor devices.

SUMMARY

To solve the above problems, various embodiments of the presentdisclosure provide a semiconductor element, wherein, a metal protectivelayer and a metal oxide protective layer are formed on the substrate toprevent the Si substrate surface from forming an amorphous layer; and atransition layer is formed to reduce lattice difference between themetal oxide protective layer and the III-IV-group buffer layer, thusimproving crystal quality of the III-IV-group buffer layer. Someembodiments of the present disclosure also provide a fabrication methodto avoid formation of amorphous layers and cracks surrounding the Sisubstrate surface. Meanwhile, a LED element or a transistor element isformed by depositing a high-quality multi-layer buffer structure via PVDand forming a GaN layer, an InGaN layer or an AlGaN layer thereon.

Technical approaches of some embodiments disclosed herein can include: asemi-conductor element, comprising a Si substrate, a multi-layer bufferstructure and an epitaxial function layer, wherein, the multi-layerbuffer structure comprises a metal protective layer, a metal oxideprotective layer, a transition layer and an III-IV-group buffer layer insequence; in which, the metal protective layer and the metal oxideprotective layer prevent the Si substrate surface from forming anamorphous layer; and the transition layer reduces lattice differencebetween the metal oxide protective layer and the III-IV-group bufferlayer, thus improving crystal quality of the III-IV-group buffer layer.

In some embodiments, the metal protective layer is made of aluminum withthickness of 1˜100 Å.

In some embodiments, the metal oxide protective layer is made ofaluminum oxide with a thickness of 1˜500 Å.

In some embodiments, the transition layer is made of oxygen-doped AlN,with oxygen-doping concentration of ≧1×10¹⁹cm⁻³.

In some embodiments, the III-IV-group buffer layer is made ofoxygen-doped AlN, with oxygen-doping concentration of ≦4×10²²cm⁻³.

Some embodiments of the present disclosure also provide a method forfabricating the semiconductor element structure by forming a multi-layerbuffer structure and an epitaxial function layer on the Si substrate,wherein, the multi-layer buffer structure is formed by:

depositing a metal protective layer on the Si substrate surface via PVD;

feeding oxygen to oxidize the upper surface of the metal protectivelayer, and depositing a metal oxide protective layer on the metalprotective layer via PVD;

keeping feeding of oxygen and feeding nitrogen, and depositing atransition layer on the surface of the metal oxide protective layer viaPVD;

stop feeding oxygen, and keeping feeding of nitrogen, and depositing anIII-IV-group buffer layer on the transition layer surface via PVD toform a multi-layer buffer structure.

In some embodiments, the metal protective layer is made of aluminum withthickness of 1˜100 Å.

In some embodiments, the metal oxide protective layer is made ofaluminum oxide with thickness of 1˜500 Å.

In some embodiments, the transition layer is made of oxygen-doped AlNwith oxygen concentration of ≧1×10¹⁹cm⁻³ and thickness of 1˜1000 nm.

In some embodiments, the transition layer is made of oxygen-doped AlNwith oxygen concentration of ≧1×10¹⁹cm⁻³ and thickness of 5˜50 nm.

In some embodiments, the III-IV-group buffer layer is made ofoxygen-doped AlN with an oxygen concentration of ≦4×10²²cm⁻³ and athickness of 10—1000 nm.

In some embodiments, the III-IV-group buffer layer is made ofoxygen-doped AlN with oxygen concentration of ≦4×10²²cm⁻³ and thicknessof 200˜300 nm.

In some embodiments, oxygen-doping concentration of the transition layeris higher than that of the III-IV-group buffer layer.

In some embodiments, the epitaxial function layer is a GaN-based LEDepitaxial layer or an AlGaN transistor epitaxial layer.

In another aspect, a system is provided including a plurality of thesemiconductor elements described above. In the case that thesemiconductor element comprises an LED element, the system can be alight-emitting system used for lighting, signage, display, etc.

At least some of the embodiments of the present disclosure can have atleast one or more of the following advantageous effects:

1. In some embodiments, a metal protective layer and a metal oxideprotective layer are formed to prevent the Si substrate surface fromforming an amorphous layer, thus avoiding cracks and poles, and furtherpreventing Ga in subsequent Ga-containing nitride from corroding the Sisubstrate through the poles, and degrading performance of semiconductordevices; and a transition layer is formed to reduce lattice differencebetween the metal oxide protective layer and the III-IV-group bufferlayer, thus improving crystal quality of the III-IV-group buffer layer.

2. When the multi-layer buffer structure is deposited via PVD, as thesputtered atoms have high energy and migration rate, the deposited filmlayers outperform those formed via conventional CVD and therebyobtaining a buffer layer interface with high flatness; when GaN, AlGaNor InGaN film layer is then formed thereon, dislocation and defectdensity are greatly reduced, thus reducing electric leakage, andimproving crystal quality and reliability of nitride semiconductordevices. As a result, the luminous efficiency and electron mobility ofthe entire light-emitting semiconductor device are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and constitute a part of thisspecification, together with the embodiments, are therefore to beconsidered in all respects as illustrative and not restrictive. Inaddition, the drawings are merely illustrative, which are not drawn toscale.

FIG. 1 is first structural diagram of a semiconductor structure ofEmbodiment 1.

FIG. 2 is a structural diagram of multi-layer buffer structure ofEmbodiment 1.

FIG. 3 is second structural diagram of a semiconductor structure ofEmbodiment 1.

FIG. 4 is a structural diagram of a semiconductor structure ofEmbodiment 2.

In the drawings: 10. Si substrate; 20. multi-layer buffer structure; 21.metal protective layer; 22. metal oxide protective layer; 23. transitionlayer; 24. III-IV-group buffer layer; 30. epitaxial function layer; 31.first semiconductor layer; 32. light-emitting layer; 33. secondsemiconductor layer; 34. non-doping semiconductor layer; 35. AlGaNlayer; 36. GaN semiconductor layer; 37. AlGaN semiconductor layer; 38.GaN semiconductor covering layer.

DETAILED DESCRIPTION

The embodiments of the present disclosure will be described in detailwith reference to the accompanying drawings and embodiments.

Embodiment 1

Referring to FIGS. 1 and 2, this embodiment provides a semiconductorelement, comprising: a Si substrate 10, a multi-layer buffer structure20 and an epitaxial function layer 30, wherein, the epitaxial functionlayer 30 is a LED epitaxial layer composed of a first semiconductorlayer 31, a light-emitting layer 32 and a second semiconductor layer 33;the first semiconductor layer 31 is a semiconductor layer doped withdonor impurity, and the second semiconductor layer 33 is a semiconductorlayer doped with acceptor impurity. The semiconductor element accordingto some embodiments can also comprise a non-doping semiconductor layer34 (Referring to FIG. 3). The multi-layer buffer structure 20 iscomposed of a 1˜100 Å metal protective layer 21, a 1˜500 Å metal oxideprotective layer 22, a 1˜1,000 nm transition layer 23 and a 10˜1,000 nmIII-IV-group buffer layer 24. In this embodiment, a 5˜50 nm transitionlayer 23 and a 200˜300 nm III-IV-group buffer layer 24 are preferred.Materials of the metal protective layer 21, the metal oxide protectivelayer 22, the transition layer 23 and the III-IV-group buffer layer 24are aluminum, aluminum oxide, oxygen-doped AlN with oxygen concentrationof ≧1×10¹⁹cm⁻³ and oxygen-doped AlN with oxygen concentration of≦10×10²²cm⁻³, wherein, to improve crystal quality ofsubsequently-deposited epitaxial layer, in this embodiment,oxygen-doping concentration of the transition layer 23 is higher thanthat of the III-IV-group buffer layer 24.

As a small amount of oxygen would be doped during depositing of an AlNbuffer layer via conventional PVD, the Si substrate 10 is likely to beoxidized; therefore, when the AlN buffer layer containing micro oxygenis directly deposited on the surface of the Si substrate 10, the Sisubstrate 10 surface is oxidized into an amorphous silicon oxide layer.This amorphous silicon oxide layer leads to poor quality of the contactsurface between the subsequently-deposited AlN buffer layer and thesubstrate 10, easy to generate cracks that degrade quality of thesemiconductor devices; meanwhile, the amorphous silicon oxide layerlowers density of the AlN buffer layer and generates holes. Insubsequent depositing of a Ga-containing nitride layer via MOCVD, Gawould corrode the Si substrate through the holes and form pits, whichlead to poor performance of semiconductor devices. In the multi-layerbuffer structure 20 of this embodiment, an Al protective layer 21 coverson the surface of the Si substrate 10 to prevent the Si substrate 10surface from being oxidized as its direct contact with oxygen isblocked; then an aluminum oxide layer 22 is deposited to mitigate the Alprotective layer 21 from being oxidized in subsequent depositing, whichfurther protects the surface of the Si substrate 10 and avoids formationof an amorphous layer; then, a transition layer 23 with oxygen-dopingconcentration ≧1×10¹⁹cm⁻³ and an III-IV-group buffer layer 24 withoxygen-doping concentration ≦4×10²²cm⁻³ are formed, wherein, thetransition layer 23 effectively reduces lattice difference between thealuminum oxide layer 22 and the III-IV-group buffer layer 24, andimproves crystal quality of the III-IV-group buffer layer 24, thusreducing internal crystal defects and dislocation of thesubsequently-deposited epitaxial layer and improving performance thesemiconductor.

To achieve the above structure and function, some embodiments of thepresent disclosure provide a method for fabricating the semiconductorepitaxial structure by forming a multi-layer buffer structure and anepitaxial function layer on the Si substrate, wherein, the multi-layerbuffer layer can be formed by a process including one or more of thefollowing steps.

First, providing a Si substrate 10 and putting it in a PVD chamber;cleaning the surface of the Si substrate 10 to remove impurities; inthis step, the substrate 10 surface is cleaned with self-bias RFsputtering method under high temperature H2 or inert gas; wherein, inertgas is any one of argon, helium or neon. In this embodiment, argon ispreferred.

Next, depositing a metal protective layer 21 on the Si substrate 10surface via PVD; wherein, the metal protective layer 21 is made ofaluminum; in this embodiment, magnetron sputtering is preferred.

Feeding oxygen to oxidize the upper layer of the metal protective layer21, and depositing a metal oxide protective layer 22 on the surface ofthe metal protective layer 21 via PVD; wherein, the metal oxideprotective layer 22 is made of aluminum oxide.

Keeping feeding of oxygen and feeding nitrogen, feeding a transitionlayer 23 on the metal oxide protective layer 22 via PVD, wherein, thetransition layer is made of oxygen-doped AlN material with oxygenconcentration of ≧1×10¹⁹cm⁻³.

Last, stop feeding oxygen, and keep feeding of nitrogen; then,depositing an III-IV-group buffer layer 24 made of oxygen-doped AlNmaterial on the transition layer 23 surface via PVD to form amulti-layer buffer structure 20; wherein, oxygen concentration of theIII-IV-group buffer layer 24 is ≦1×10²²cm⁻³;

The multi-layer buffer structure 20 formed through this method featureshigh crystal quality and flat interface. The dislocation, defect densityand electric leakage of subsequently-formed Ga-containing LED aregreatly reduced, thus improving device reliability and luminousefficiency of the entire light-emitting semiconductor device.

Embodiment 2

Referring to FIG. 4, difference between this embodiment and Embodiment 1may include, a transistor epitaxial layer is deposited on the surface ofthe multi-layer buffer structure 20 as the epitaxial function layer 30,so as to form a transistor element. The fabrication method is structureis as follows: put the substrate of the multi-layer buffer structure 20deposited with the metal protective layer 21, the metal oxide protectivelayer 22, the transition layer 23 and the III-IV-group buffer layer 24into the MOCVD chamber, and deposit an AlGaN layer 35 via MOCVD tofurther mitigate lattice stress of the multi-layer buffer structure 20and avoid cracks; then, deposit an unintentionally doped or C-doped orFe-doped GaN semiconductor layer 36, and then an AlGaN semiconductorlayer 37, wherein, the AlGaN semiconductor layer 37 generateshigh-density electron gas at interface through electric fieldpolarization; and finally, deposit an GaN semiconductor covering layer38, wherein, the covering layer 38 acts as a contact layer, to fabricateelectrode and finally form a transistor element.

All references referred to in the present disclosure are incorporated byreference in their entirety. Although specific embodiments have beendescribed above in detail, the description is merely for purposes ofillustration. It should be appreciated, therefore, that many aspectsdescribed above are not intended as required or essential elementsunless explicitly stated otherwise. Various modifications of, andequivalent acts corresponding to, the disclosed aspects of the exemplaryembodiments, in addition to those described above, can be made by aperson of ordinary skill in the art, having the benefit of the presentdisclosure, without departing from the spirit and scope of thedisclosure defined in the following claims, the scope of which is to beaccorded the broadest interpretation so as to encompass suchmodifications and equivalent structures.

1. A semiconductor element, comprising: a Si substrate, a multi-layerbuffer structure, and an epitaxial function layer, wherein: themulti-layer buffer structure comprises a metal protective layer, a metaloxide protective layer, a transition layer, and a III-IV-group bufferlayer in sequence; wherein the metal protective layer and the metaloxide protective layer are configured to prevent the Si substratesurface from forming an amorphous layer; and the transition layer isconfigured to reduce a lattice difference between the metal oxideprotective layer and the III-IV-group buffer layer, thereby improvingcrystal quality of the III-IV-group buffer layer.
 2. The semiconductorelement according to claim 1, wherein the metal protective layer is madeof aluminum with a thickness of 1˜100 Å.
 3. The semiconductor elementaccording to claim 1, wherein the metal oxide protective layer is madeof aluminum oxide with a thickness of 1˜500 Å.
 4. The semiconductorelement according to claim 1, wherein the transition layer is made ofoxygen-doped AlN, with an oxygen-doping concentration of ≧1×10¹⁹cm. 5.The semiconductor element according to claim 1, wherein the III-IV-groupbuffer layer is made of oxygen-doped AlN, with an oxygen-dopingconcentration of ≦4×10²²cm⁻³.
 6. A method for fabricating asemiconductor element structure by forming a multi-layer bufferstructure and an epitaxial function layer on the Si substrate, wherein,the multi-layer buffer structure is formed by: depositing a metalprotective layer on the Si substrate surface via physical vapordeposition (PVD); feeding oxygen to oxidize the upper surface of themetal protective layer, and depositing a metal oxide protective layer onthe metal protective layer via PVD; keeping feeding of oxygen andfeeding nitrogen, and depositing a transition layer on the surface ofthe metal oxide protective layer via PVD; stop feeding oxygen, andkeeping feeding of nitrogen, and depositing an III-IV-group buffer layeron the transition layer surface via PVD to form a multi-layer bufferstructure.
 7. The method for fabricating a semiconductor elementaccording to claim 6, wherein the metal protective layer is made ofaluminum with thickness of 1˜100 Å.
 8. The method for fabricating asemiconductor element according to claim 6, wherein the metal oxideprotective layer is made of aluminum oxide with thickness of 1˜500 Å. 9.The method for fabricating a semiconductor element according to claim 6,wherein the transition layer is made of oxygen-doped AlN with oxygenconcentration of ≧1×10¹⁹cm⁻³ and thickness of 1˜1000 nm.
 10. The methodfor fabricating a semiconductor element according to claim 6, whereinthe transition layer is made of oxygen-doped AlN with oxygenconcentration of ≧1×10¹⁹cm⁻³ and thickness of 5˜50 nm.
 11. The methodfor fabricating a semiconductor element according to claim 6, whereinthe III-IV-group buffer layer is made of oxygen-doped AlN, with anoxygen-doping concentration of ≦4×10²²cm⁻³ and a thickness of 10˜1000nm.
 12. The method for fabricating a semiconductor element according toclaim 6, wherein the III-IV-group buffer layer is made of oxygen-dopedAlN, with oxygen-doping concentration of ≦4×10²²cm⁻³ and a thickness of200˜300 nm.
 13. The method for fabricating a semiconductor elementaccording to claim 6, wherein an oxygen-doping concentration of thetransition layer is higher than that of the III-IV-group buffer layer.14. The method for fabricating a semiconductor element according toclaim 6, wherein: the epitaxial function layer is a light-emitting diode(LED) epitaxial layer or a transistor epitaxial layer.
 15. Alight-emitting system comprising a plurality of semiconductor elements,each element comprising: a Si substrate, a multi-layer buffer structure,and an epitaxial function layer, wherein: the multi-layer bufferstructure comprises a metal protective layer, a metal oxide protectivelayer, a transition layer, and a III-IV-group buffer layer in sequence;wherein the metal protective layer and the metal oxide protective layerare configured to prevent the Si substrate surface from forming anamorphous layer; and the transition layer is configured to reduce alattice difference between the metal oxide protective layer and theIII-IV-group buffer layer, thereby improving crystal quality of theIII-IV-group buffer layer.
 16. The system according to claim 15, whereinthe metal protective layer comprises aluminum with a thickness of 1˜100Å.
 17. The system according to claim 15, wherein the metal oxideprotective layer comprises aluminum oxide with a thickness of 1˜500 Å.18. The system according to claim 15, wherein the transition layercomprises oxygen-doped AlN, with an oxygen-doping concentration of≧1×10¹⁹cm.
 19. The system according to claim 15, wherein theIII-IV-group buffer layer comprises oxygen-doped AlN, with anoxygen-doping concentration of ≦4×10²²cm⁻³.
 20. The system according toclaim 15, wherein each semiconductor element is fabricated by forming amulti-layer buffer structure and an epitaxial function layer on the Sisubstrate, wherein, the multi-layer buffer structure is formed by:depositing a metal protective layer on the Si substrate surface viaphysical vapor deposition (PVD); feeding oxygen to oxidize the uppersurface of the metal protective layer, and depositing a metal oxideprotective layer on the metal protective layer via PVD; keeping feedingof oxygen and feeding nitrogen, and depositing a transition layer on thesurface of the metal oxide protective layer via PVD; stop feedingoxygen, and keeping feeding of nitrogen, and depositing an III-IV-groupbuffer layer on the transition layer surface via PVD to form amulti-layer buffer structure.